The invention relates to a device to feed intermittently viscous lubricants to sliding surfaces, in particular to introduce grease into the body of a power chuck mounted on a machine tool.
In chucks, the lubricant is usually introduced into the jaw ways by means of a lubricant dispenser designed as graase gun and placed over a lubricating nipple installed in the chuck body and communicating with the lubricating slots through a canal so that lubricant is pressed into the lubricating slots, in most cases inan undefined quantity, by the action of a delivery element upon a supply container. The time interval between the various lubricating processes to be performed manually is not defined either, but is up to the discretion of the person servicing the lathe. The result, therefore, is an improper and insufficient, often irregular lubrication of the jaw ways. This, in turn, can lead to damage to the jaws and/or to the chuck body, and thus to production interruptions.
In a power chuck, it is known through DE-OS No. 32 20 585 to assign to each of the jaws a lubricant dispenser, each consisting of a lubricant filled supply container in the form of a lubricant cartridge disposed in the chuck body and of a delivery element designed as a moving piston inserted in said lubricant cartridge, acted upon by pressure medium and acting upon the lubricant. To have the moving piston acted upon in selectable time intervals, there is intalled in a connecting canal a control valve by means of which the connecting canal can be unblocked. In addition, for controlled action upon the face of the control valve, a two-way valve actuatable in settable time intervals is provided. While this design, by means of which the jaw ways are supplied with lubricant in regular time intervals or as a function of a certain operating position automatically and sufficiently has proven out well, it is an expensive one because a multiplicity of recesses and canals has to be machined into the chuck body. Furthermore, installing filled cartridges, each of which must be exchanged individually, into the power chuck is very time-consuming.
Accordingly, it is an object of the invention to create a device which can be readily coupled to a component and by means of which viscous lubricant can be fed to sliding surfaces automatically and intermittently without incurring high production costs, in particular for the component containing the sliding surfaces to be lubricated. There should also be assurance of great operating reliability and that the lubricant transfer is performed in a short period of time without dirt getting into the lubricant or into components conducting or receiving it.
According to the invention, this is achieved by an externally disposed supply container which contains the lubricant and is equipped with a delivery plunger which can constantly be acted upon by pressure medium, and by a lubricating head which is connected to said supply container via a flexible line, is stationarily held a short distance from the chuck body, can be acted upon by pressure medium, can be coupled to a lubricant canal machined into the chuck body for lubricant transfer and is equipped with a pressure intensifier actuatable in selectable time intervals.
It is expedient to equip the supply container with a control device to monitor its fill level, which device may consist, in a simple embodiment, of a differential piston which is connected to the delivery plunger of the supply container so as to be movable within limits and is automatically movable by said delivery plunger in an end position range, and of a sensor such as in the form of a proximity switch actuatable by said differential piston. In addition, the differential piston should be installed in a recess machined into a removable cover of the supply container so as to be movable against the force of a spring, and it should have a piston rod or a similar extension permanently attached to it and going to the outside, on which is mounted a pulse generator such as in the manner of a switching ring which interacts with a proximity switch fixed preferably to the cover of the supply container.
It is further expedient for the delivery plunger to be movably guided on a piston rod which is fastened to the differential piston and projects into the interior of the supply container, and to provide a stop such as in the form of an inserted stop ring on said piston rod in the latter's end area, the delivery plunger interacting with said stop ring to move the differential piston and the switching ring connected to it.
The lubricating head should consist of a pressure piston which is installed in a stationary housing, can be acted upon by pressure medium in time intervals and is movable by the pressure medium in the direction of the chuck body countering the force of one or more return springs, and of a displacement piston movably held in the former, both pistons enclosing a pressure chamber connectable to the supply container and to the lubricant canal machined into the chuck body, and both pistons being movable relative to each other for the intensification of the lubricant pressure.
The pressure chamber should further be preceded by a check valve preferably installed in the pressure piston, and the pressure chamber should be provided with a shutoff valve which is installed in the displacement piston and opens due to the latter making contact with the chuck body or as a function of the lubricant pressure.
To set the amount of lubricant to be introduced into the chuck body it is expedient to provide the pressure piston with a preferably steplessly adjustable stop, by means of which its travel can be limited. This stop may consist of a ring screwed to an extension projecting out of the housing accommodating it. It is further advantageous in this embodiment to dispose the return spring associated with the pressure piston between the housing accommodating the pressure piston and the stop.
To assure always a reliable lubricant transfer, the chuck body should be equipped with a plane bearing surface surrounding the lubricant canal machined into the chuck body to support the displacement piston. In addition, it is expedient to close the lubricant canal of the chuck body towards the outside by a check valve and to dispose the lubricating head behind a cover of the machine tool supporting the power chuck and to fasten it to the machine tool spindle head.
The lubricant dispenser designed in accordance with the invention is not only simple in its construction and, therefore, producible economically, it is also operationally reliable in its function, making it possible, above all, to lubricate all sliding surfaces of a power chuck or of a similar part, simultaneously and sufficiently in a short period of time. The device thus consists of a supply container filled with lubricant and equipped with a delivery piston constantly acted upon by pressure medium and of a lubricating head connected thereto and containing a pressure intensifier which can be actuated in selectable time intervals and can be coupled to a lubricant canal for the transfer of lubricant. Because of this, there is assurance that the lubricant can be introduced into a component such as a power chuck under high pressure and in a short time. Consequently, all lubrication points connected to a preferably central lubricant canal can be supplied with lubricant reliably, simultaneously and adequately so that satisfactory lubrication is assured at all times and operating problems caused by insufficient lubrication are thus avoided, especially also as the amount of lubricant in the supply container is being monitored.